Silicon nitride layers (SiNx), for example those deposited by a Low Pressure Chemical Vapor Deposition (LPCVD) method among insulating materials during semiconductor fabrication processes, have been widely used because of their excellent reactive ion etching (RIE) and wet etching selectivities with respect to silicon oxide layers, their abrasion resistance, their oxidation resistance, and their properties as a diffusion barrier. However, SiNx layers have a relatively high dielectric constant of about 7, so that parasitic capacitance may increase when a device is scaled down in size, which may cause propagation delay.
In recent years, boron nitride (BN) layers have been used as an insulating layer of semiconductor devices. BN layers have a dielectric constant that is generally lower than LPCVD SiNx layers. Typically, BN layers are deposited at a low temperature of about 200° C. to 550° C. by an atomic layer deposition (ALD) method, so that a conformal stoichiometric boron nitride layer can be formed.
BN layers deposited by the ALD method typically have a low dielectric constant of about 2.2 to about 5, according to the deposition condition. Thus, the parasitic capacitance of BN layers may be reduced compared to SiNx layers having a dielectric constant of 7, thereby reducing propagation delay.
However, BN layers deposited by the ALD method may be hydrolyzed by moisture in the air, easily etched by a H2SO4-based high temperature wet chemical etch, and may have poor oxidation resistance.